CV Axle Problem

[Mayolives]

I installed a pair of rebuilt cv axles in my used R200 lsd differential and after a short session on a road course track, my car acted as if the transmission was not in gear and/or I had lost the clutch. The car would not move. After being towed to my pit area, I discovered the drive shaft was turning when the transmission was engaged but the rear wheels were not moving. My first thought was a differential problem, but upon further tear down and inspection, I discovered a broken cv axle. The joint near the differential was in pieces. I purchased the rebuilt cv axles from Modern-motorsports and what occurred happened on their first trip under a load. My question is, why did the car not move with only one broken cv axle? Why didn't the other axle propel the car? I haven't opened the differential but I did drain the gear oil and it was clean and new. Any thoughts on the condition of my lsd? Is it ok? Did I get a bad cv axle from Modern-motorsports?

[JMortensen]

LSD only "limits" slip. If you have one tire with no traction at all, or in your case if you have a broken CV shaft, the diff will spin. Get your new CV shaft in then try to turn the tires in different directions by hand. You'll know right away if the LSD is broken.

[RTz]

I'll second Jon... It would take a preload setting way beyond usable to expect the car to move about on one axle.

[Modern Motorsports Ltd]

Tom, great to hear you got the car together now! I'm assuming this is same package we sent out Mar/05 and then discussed some install details with your install shop in Aug. same year?

 

Are you certain yourself or the shop completed the typical Z31CV axle shortening procedure on your axles? If not they could easily see compression travel limit and a failure could then occur. Send me your current email and I can resend the PDF we sent you in Dec/04 if you need the quick DIY bench shortening info. Those same type axles have tolerated 9.3 second 1/4 mile passes (3.3 0-60 ft) on one of our Australian customer's Nissan's. Typical conditions should not cause any issue with the Z31 CV's, they've been very well proven as an excellent Z car solution.

 

Feel free to drop us a direct email to discuss this further if you like. We can help source a used replacement or build a new center custom billet bar etc. Not too far from you, Roger at www.zbarn.com may have some available, he's an excellent reputable and very fair source for used Z parts we often refer customers to for cores etc.

 

PS, as I recall, factory clutch type LSD's had a typical preload of ~35-40 ft-lbs. (with car in the air, and one wheel locked, only takes 35 ft-lbs force to break free your other wheel from the LSD clutch action). Autox's (I know Ron did this at least once right Ron?) may wish to have this tightened up to a higher limit approaching 90 or 100 but with that comes quicker clutch wear as well and the LSD clutches are a pricey replacement item. Hopefully your LSD is fine. We did just have one 3.7 R200 clutch type LSD come available by a customer upgrading his rear to billet components and a quaife setup if indeed you do require a clutch type LSD.

 

Either way please do let us know what you discover and if we can help, cheers.

[Mayolives]

Ross,

Yes, I did the reversal, shortening procedure on both axles before I installed them. Is it possible that you had already shortened them and I inadvertently reversed them back into the longer position? As I remember it, the axles had a very "snug" fit when I installed them. Thanks for your help, Tom.

[RTz]

PS' date=' as I recall, factory clutch type LSD's had a typical preload of ~35-40 ft-lbs. (with car in the air, and one wheel locked, only takes 35 ft-lbs force to break free your other wheel from the LSD clutch action). Autox's (I know Ron did this at least once right Ron?) may wish to have this tightened up to a higher limit approaching 90 or 100[/quote']

 

 

Ross,

Pretty well nailed it. The production car diffs ran, as you say, 35-45 and the last NISMO comp. diff I bought was close to 55. Nissan diffs are pretty easy to adjust and its necessary for a track car. How much depends on car set-up and driver preference... at minimum 55lbs. Go up from there.

 

Tom,

Very nice car! The fact you car didn't move one on axle isn't cause for alarm... especially if its a production car diff thats never been shimmed. The significant portion of the 'lock-up' comes from the side gears separating, putting pressure on the clutches. In order for the side gears to separate they have to have something to work against. Essentially, that comes from two places... what little grip is left on the inside tire and the pre-load on the clutches. The inside rear, generally speaking, dosent have enough grip to work against, hence the 'help' from the pre-load. However pre-load, on its own, isn't enough either unless its substantial. So the typical LSD, if you raise one wheel off the ground, won't provide much torque at all to the other. In normal conditions, once the reaction has begun, the amount of 'lock-up' can be substantial.

[JMortensen]

I have a pretty good thread on shimming the LSD here: http://forums.hybridz.org/showthread.php?t=92629

 

If the stock unit has a weakness its that there is only one clutch disk and two clutch plates to transfer the torque on each side. Some of the NISMO units have a lot more clutches in them, more like 8 per side IIRC and more aggressive ramps too for better lockup. However you'll see in that thread that a roadster racer bought an LSD from Nissan Comp directly and got the big spacers, so from what I can tell it's a bit of a crap shoot.

 

If you did break yours Tom, I'd suggest a KAAZ or Cusco diff as they have a lot more and larger clutches than even the "good" NISMO LSD, and they run in the $800 range online.